The current study sought to assess the importance of three common variables on the outcome of TiO(2) photocatalysis experiments with bacteria. Factors considered were (a) ability of test species to withstand osmotic pressure, (b) incubation period of agar plates used for colony counts following photocatalysis and (c) chemical nature of suspension medium used for bacteria and TiO(2). Staphylococcus aureus, Escherichia coli, Salmonella ser. Typhimurium and Pseudomonas aeruginosa were found to vary greatly in their ability to withstand osmotic pressure, raising the possibility that osmotic lysis may be contributing to loss of viability in some photocatalytic disinfection studies. Agar plate incubation time was also found to influence results, as bacteria treated with UV light only grew more slowly than those treated with a combination of UV and TiO(2.) The chemical nature of the suspension medium used was found to have a particularly pronounced effect upon results. Greatest antibacterial activity was detected when aqueous sodium chloride solution was utilised, with approximately 1 x 10(6) CFU mL(-1)S. aureus being completely killed after 60 min. Moderate activity was observed when distilled water was employed with bacteria being killed after 2h and 30 min, and no antibacterial activity at all was detected when aqueous tryptone solution was used. Interestingly, the antibacterial activity of UV light on its own appeared to be very much reduced in experiments where aqueous sodium chloride was employed instead of distilled water.

Silicone rubber sheeting can be used as a passive sampling device for hydrophobic organic contaminants in the environment to determine the available concentrations in water and sediments. Reliable sampler-water partition coefficients are required to 12 determine the sampling rates and the dissolved contaminant concentrations in water and in sediment pore water. Log partition coefficients (log w sr K , ) for silicone rubber-water 14 have been estimated for 32 polycyclic aromatic hydrocarbons (PAHs), 2 deuterated PAH 15 analogues and 32 chlorobiphenyls (CBs) using the cosolvent method, with methanol as 16 cosolvent. Strong linear relationships were found with literature values for the 17 corresponding log octanol-water partition coefficients (log ow K ) for both CBs and PAHs, confirming that partitioning into the silicone rubber is strongly determined by the hydrophobicity of the compounds, which suggests log ow K is a good predictor of log w sr K , and that absorption is the main mechanism for accumulation of analytes into the silicone rubber polymer.

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